Super Hot Cores in NGC 253: Witnessing the formation and early evolution of Super Star Clusters

Abstract

Using $0.2^{\prime \prime }$ ($\sim 3$ pc) ALMA images of vibrationally excited HC${}_3$N emission (HC${}_3$N${}^{\ast }$) we reveal the presence of $8$ unresolved Super Hot Cores (SHCs) in the inner $160$ pc of NGC\,253. Our LTE and non-LTE modelling of the HC${}_3$N${}^{\ast }$ emission indicate that SHCs have dust temperatures of $200-375$ K, relatively high H${}_2$ densities of $1-6\times 10^6$ cm${}^{-3}$ and high IR luminosities of $0.1-1\times 10^8$ L${}_{\odot }$. As expected from their short lived phase ($\sim 10^4$ yr), all SHCs are associated with young Super Star Clusters (SSCs). We use the ratio of luminosities form the SHCs (protostar phase) and from the free-free emission (ZAMS star phase), to establish the evolutionary stage of the SSCs. The youngest SSCs, with the larges ratios, have ages of a few $10^4$ yr (proto-SSCs) and the more evolved SSCs are likely between $10^5$ and $10^6$ yr (ZAMS-SSCs). The different evolutionary stages of the SSCs are also supported by the radiative feedback from the UV radiation as traced by the HNCO/CS ratio, with this ratio being systematically higher in the young proto-SSCs than in the older ZAMS-SSCs. We also estimate the SFR and the SFE of the SSCs. The trend found in the estimated SFE ($\sim 40\%$ for proto-SSCs and $>85\%$ for ZAMS-SSCs) and in the gas mass reservoir available for star formation, one order of magnitude higher for proto-SSCs, suggests that star formation is still going on in proto-SSCs. We also find that the most evolved SSCs are located, in projection, closer to the center of the galaxy than the younger proto-SSCs, indicating an inside-out SSC formation scenario.

typos corrected, references added

References in corpus (12)

• Tracing shocks and photodissociation in the Galactic center region
• Spectral Line Identification and Modelling (SLIM) in the MAdrid Data CUBe Analysis (MADCUBA) package: An interactive software for data cube analysis
• The formation of ethylene glycol and other complex organic molecules in star-forming regions
• High-Resolution Radio Continuum Measurements of the Nuclear Disks of Arp 220
• The Physical Conditions in a Pre Super Star Cluster Molecular Cloud in the Antennae Galaxies
• ALMA observations of 99 GHz free-free and H40$\alpha$ line emission from star formation in the centre of NGC 253
• Modeling the H2O submillimeter emission in extragalactic sources
• The nucleus of NGC 253 and its massive stellar clusters at parsec scales
• The Greenhouse Effect in Buried Galactic Nuclei and the Resonant HCN Vibrational Emission
• Diverse nuclear star-forming activities in the heart of NGC 253 resolved with ten-pc scale ALMA images
• Origin of the ionized wind in MWC 349A
• The Youngest Globular Clusters

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